The decision is not yet final as parties to the procedure have 30 days to lodge any complaints.

Several green NGOs have been staunchly opposed to the project but their complaints against the first-instance decision by the Environment Agency have been thrown out.

It remains unclear whether they will also challenge this decision.

Petrol Geoterm, a subsidiary of the energy group Petrol, said the refinery could become operational within a year.

It would be used to process gas from the Petišovci oil field, which is estimated to hold 50-80 million cubic metres of natural gas.

While environmentalists have mounted strong opposition against fracking as the extraction method, the licence holders have said the method used would not be fracking but much less dangerous hydraulic stimulation of slate.

The project is being carried out in conjunction with Ascent Resources, a UK gas extraction specialist, and Geoenergo, another Petrol group company.